The present invention relates generally to pressure gauge indicators and, more particularly, to a mechanical single-turn indicator for showing the position of a multiple-turn actuator which might be used for example, in a regulating valve for regulation of downstream pressure.
Regulating valves are used in the irrigation industry for maintaining a predetermined downstream pressure. The regulating valve receives a small pilot supply of water from a main fluid supply valve. The regulating valve controls the pressure within a closure chamber of the main fluid supply valve, to thereby cause the main fluid supply valve to pass water from an upstream pipe to a downstream pipe when a pressure in the downstream pipe falls below a predetermined pressure. The flow of water through the main fluid supply valve is thus controlled by the regulating valve to achieve a desired downstream pressure.
In order to determine whether the desired downstream pressure has been achieved, a pressure gauge can be attached to the regulating valve to thereby indicate the downstream pressure. Since pressure gauges can be expensive, a common practice in the irrigation industry is to attach a Schrader valve to the regulating valve. The Schrader valve can accommodate a pressure hose gauge assembly, which can be connected to the Schrader valve for downstream pressure checks and adjustments.
Although use of a Schrader valve in combination with a regulating valve can be cost effective, this combination can also be labor intensive. During system checks, walk throughs, and other procedures where the downstream pressure of a regulating valve needs to be monitored, the user must carry the pressure hose gauge assembly and manually attach the pressure hose gauge assembly to each Schrader valve before reading the downstream pressure of the regulating valve. Thus, the user can only determine the downstream pressure of the regulating valve after connecting the pressure hose gauge assembly to the Schrader valve. A simple task of checking the downstream pressures of 10 regulating valves can consume a large amount of time, when the user is forced to attach the pressure hose gauge assembly to the Schrader valve of each regulating valve before reading the pressure of that regulating valve.
Another solution proposed by the prior art involves fitting the pressure gauge directly onto either the regulator valve or the downstream pipe. This solution, however, usually requires a significant financial expenditure for purchasing a pressure gauge and regulating valve combination. Such a combination of a pressure gauge and regulating valve is typically about double the cost of the above-mentioned Schrader valve and pressure hose gauge assembly combination. Additionally, many contractors do not recommend putting a sensitive pressure gauge into the regulating valve box.
U.S. Pat. No. 2,379,517 to E. L. Haden, issued on Jul. 3, 1945, discloses a universal indicator for remote controlled deck sockets. The indicator is basically a two position indicator for communicating whether a valve is in an open or closed position. This device uses an annular nut moveable relative to a rotatable spindle and having a single pin attached thereto.
When the spindle is rotated, the pin of the nut travels along a single helical slot to rotate a stationary sleeve. As the pin travels within the helical slot of the stationary sleeve, the pin also exerts a rotational force on a corresponding vertical slot of a corresponding oscillating sleeve.
Only the single pin, and the corresponding single helical slot are used, to rotate the oscillating sleeve. As a result, rotational force is only applied to a single point of the oscillating sleeve. Application of the rotational force to the oscillating sleeve at only a single point tends to cause an imbalanced motion, and further results in a frictional operation.
Another shortcoming of this prior art apparatus is the positioning of the helical slot on the stationary sleeve and the positioning of the vertical slots on the oscillating sleeve. Since the purpose of the pin of the annular nut is to rotate the oscillating sleeve with minimal friction, placement of vertical slots on the oscillating sleeve (as opposed to helical slots, for example) causes added friction. Thus, the primary sources of friction result from use of only a single pin of the annular nut, and from use of only a single vertical slot within the oscillating sleeve. The unbalanced forces resulting from use of only a single pin and a vertical slot may actually generate jamming forces.
Perhaps one result of this unbalanced force-application system of the prior art is the very limited range of motion of the index mark of the Haden device. Basically, this index mark moves within a range of approximately 30 degrees along a circle to indicate whether the valve is open or shut. The limited display of information, indicating only whether the valve is open or shut, is itself a shortcoming of the prior art as well. A device of simple and low-friction construction is thus needed for displaying a range of pressures of the regulating valve.
A result of the frictional operation of the Haden prior art device is that this device may need to be manufactured in metal parts and, further, may need to be lubricated to ensure proper operation. Metal parts can be expensive, subject to rust, and heavy. Lubrication of these metal parts can increase the complexity of the system for venting air from the spring side of the regulator diaphragm, for example.
A need has thus existed in the prior art for a compact, durable, and economically feasible pressure gauge indicator, which can be permanently affixed to regulating valve to thereby avoid the large expenditure of time associated with assembly and disassembly of Schrader-valve compatible pressure gauges.